identifier

• Obligation:  See Application Profiles
• Occurrence:  See Application Profiles
• Conditions:  See Application Profiles
• Scheme:  See Application Profiles; see also URI [URL]

Element Semantics (Definition)

An unambiguous reference to the resource within a given context.

General

• Name:  identifier
• Label:  Identifier
• Namespace:  http://purl.org/dc/elements/1.1/
• Registration Authority:  Dublin Core Metadata Initiative (DCMI)
• Notes:  Recommended best practice is to identify the resource by means of a string or number conforming to a formal identification system. Example formal identification systems include the Uniform Resource Identifier (URI) (including the Uniform Resource Locator (URL)), the Digital Object Identifier (DOI) and the International Standard Book Number (ISBN).

Best Practices

1. The «identifier» element is used to hold values that uniquely identify the resource being described.
2. It is important to not confuse the concept of "identification" with that of "location". While some identifiers also provide a means for accessing the resource being described, others do not. For example, a URL may serve both to identify the resource and to provide access (location) while an ISSN or an ISBN identifies but does not provide access. By definition, the «identifier» element is about identification and not location.
3. Since the Dublin Core Metadata Initiative does not currently provide an element for values that identify the location of the resource, common practice relies on «identifier» values (i.e., URLs) as the means for locating and accessing the resource being described.

Metadata Encodings Examples

• Resource Description Framework (RDF/XML)
  

  Example 1:
  
  <?xml version='1.0' encoding='UTF-8'?>
  <rdf:RDF xmlns:rdf='http://www.w3.org/1999/02/22-rdf-syntax-ns#'
      xmlns:dc='http://purl.org/dc/elements/1.1/'>
  <rdf:Description>
      <dc:identifier>
      ISBN: 0-937597-57-0
      </dc:identifier>
  </rdf:Description>
  </rdf:RDF>
  
  Example 2:
  
  <?xml version='1.0' encoding='UTF-8'?>
  <rdf:RDF xmlns:rdf='http://www.w3.org/1999/02/22-rdf-syntax-ns#'
      xmlns:dc='http://purl.org/dc/elements/1.1/'>
  <rdf:Description>
      <dc:identifier rdf:resource='http://www.thegateway.org'/>
  </rdf:Description>
  </rdf:RDF>
  

• XML (Tags & Attributes)
  

  Example 1:
  
  <?xml version='1.0' encoding='UTF-8'?>
  <record xmlns:dc='http://purl.org/dc/elements/1.1/'>
  <dc:identifier>
      ISBN: 0-937597-57-0
  </dc:identifier>
  </record>
  
  Example 2:
  
  <?xml version='1.0' encoding='UTF-8'?>
  <record xmlns:dc='http://purl.org/dc/elements/1.1/'
      xmlns:dcterms='http://purl.org/dc/terms/'
      xmlns:xsi='http://www.w3.org/2001/XMLSchema-instance'>
  <dc:identifier xsi:type='dcterms:URI'>
      http://www.thegateway.org
  </dc:identifier>
  </record>
  

• Crosswalks
  IEEE LOM: 1.1:General.Identifier [Not currently used]
  MARC: 024 8#$a (Other Standard Identifier/Standard number or code)